Fiber optic connector and method

ABSTRACT

A fiber optic connector including a ferrule surrounding an optical fiber and a hub engaging the ferrule. The hub includes a front portion having first and second opposing surfaces and first and second tapered regions extending from the first and second opposing surfaces to a front face. A housing includes an anti-rotation seat configured to engage the first and second opposing surfaces, the anti-rotation seat including parallel first and second contact lines positioned at a front of the anti-rotation seat. A spring within a chamber of the housing biases the ferrule through a bore in the front of the housing. The first tapered region of the hub engages the first contact line and the second tapered region engages the second contact line when the hub and ferrule are in a first rotational position so that the optical fiber is maintained at a known orientation with respect to the connector.

BACKGROUND

Fiber optic cables are used in the telecommunication industry totransmit light signals in high-speed data and communication systems. Astandard fiber optic cable includes a fiber with an inner lighttransmitting optical core. Surrounding the fiber is an outer protectivecasing.

A fiber terminates at a fiber optic connector. Connectors are frequentlyused to non-permanently connect and disconnect optical elements in afiber optic transmission system. There are many different fiber opticconnector types. Some of the more common connectors are FC and SCconnectors. Other types of connectors include ST and D4-type connectors.

A typical SC fiber optic connector includes a housing having a front endpositioned opposite from a rear end. The front end of the SC connectorhousing is commonly configured to be inserted within an adapter. Anexample adapter is shown in U.S. Pat. No. 5,317,663, assigned to ADCTelecommunications, Inc. The SC connector typically further includes aferrule that is positioned within the front and rear ends of thehousing, and adjacent the front end. The ferrule is axially moveablerelative to the housing, and is spring biased toward the front of theconnector. The fiber optic cable has an end that is stripped. Thestripped end includes a bare fiber that extends into the connector andthrough the ferrule.

A connector, such as the connector described above, is mated to anotherconnector within an adapter like the adapter of U.S. Pat. No. 5,317,663.A first connector is received within the front portion of the adapter,and a second fiber is received within the rear portion of the adapter.When two connectors are fully received within an adapter, the ferrules(and hence the fibers internal to the ferrule) contact or are in closeproximity to each other to provide for signal transmission between thefibers. Another connector and mating adapter is shown in U.S. Pat. No.6,142,676, assigned to ADC Telecommunications, Inc.

Signal losses within a system often occur within the connection betweentwo optical fiber cores. Due to manufacturing tolerances of the ferruleouter diameter to inner diameter concentricity, ferrule inner diameterhole size and fiber outer diameter, and fiber core to fiber outerdiameter concentricity, when the fiber is inserted into the ferrule thecore of a fiber may not and typically does not end up perfectly centeredrelative to the ferrule outer diameter. If one or both of the fibers areoff center, when they are connected within an adapter, the fibers willnot be aligned and thus there will be a signal loss when the signal istransmitted between the two fibers. It may therefore be desirable totune a connector to minimize this signal loss. Tuning can beaccomplished by measuring signal characteristics through the connectorand/or by examining physical properties of the connector, and thendetermining the optimal position of the ferrule and fiber in theconnector.

Rotational misalignment of a ferrule with respect to a connector axiscan cause mis-engagement between the ferrule and a ferrule of anotherconnector, thereby contributing to signal loss. This problem isespecially acute for angled physical contact connectors. An angledphysical contact (APC) connector includes a ferrule and fiber with endfaces that are polished to a non-perpendicular angle (for example, 8degrees to a perpendicular plane) with respect to the longitudinal axisof the connector. APC connectors are discussed in U.S. Pat. No.5,734,769, assigned to ADC Telecommunications, Inc. The orientation ofthe end face must be maintained with a high degree of precision so thatthe angled end face of the optic fiber and associated ferrule correctlyengage an end face of an optic fiber and associated ferrule of anotherangled physical contact connector. Even a few degrees of misalignmentcan cause significant signal loss.

SUMMARY

The present invention concerns fiber optic connectors, including tunablefiber optic connectors, having a spring biased ferrule and hub assemblyheld within the connector. If the fiber optic connector is tunable,tuning can be accomplished unseating the ferrule and associated hub froma resting position by pressing the ferrule back into the connector sothat an anti-rotation portion of the hub clears a complementary-shapedanti-rotation seat of the connector. In this position, the ferrule canbe rotated about a connector axis to the desired rotational alignmentthat minimizes signal loss. The ferrule can then be released, allowingthe anti-rotation portion of the hub to re-engage the anti-rotationseat, thereby preventing further rotation that may cause the connectorto become un-tuned.

The anti-rotation seat further includes at least first and secondcontact lines which maintain the end face of the optic fiber andassociated ferrule at a specific rotational angle with respect to thelongitudinal axis of the connector when the ferrule is in its restingposition. Further, when the ferrule is pushed back into the connectorand then allowed to return to its resting position, the contact lines ofthe anti-rotation seat re-engage the ferrule and associated hub toreturn the end face of the optic fiber and associated ferrule to thedesired orientation.

One aspect of the invention relates to a fiber optic connector includingan optical fiber, a ferrule surrounding the optical fiber, a hubretainably engaging the ferrule, wherein the hub includes a frontportion having first and second opposing surfaces and first and secondtapered regions extending from the first and second opposing surfaces toa front face of the hub at an angle with respect to a longitudinal axisof the connector, a housing defining an anti-rotation seat configured toengage the first and second opposing surfaces of the front portion ofthe hub, the anti-rotation seat including parallel first and secondcontact lines positioned at a front of the anti-rotation seat adjacent abore defined by the housing through which the ferrule extends, and aspring disposed within a chamber defined by the housing and coupled tothe anti-rotation seat, the spring biasing the ferrule through the boreof the housing, wherein the first tapered region of the hub engages thefirst contact line and the second tapered region engages the secondcontact line when the hub and ferrule are in a first rotational positionrelative to the housing so that an end of the optical fiber ismaintained at a known orientation with respect to the longitudinal axisof the connector.

Another aspect of the invention relates to a hub and ferrule assemblyfor a fiber optic connector including a ferrule configured to surroundan optical fiber, and a hub retainably engaging the ferrule, wherein thehub includes a front portion having first and second opposing surfacesand first and second tapered regions extending from the first and secondopposing surfaces to a front face of the hub at an angle with respect toa longitudinal axis extending through a center of the hub and ferruleassembly, wherein the first tapered region is positioned to engage afirst contact line on the fiber optic connector and the second taperedregion is positioned to engage a second contact line on the fiber opticconnector.

Yet another aspect of the invention relates to a fiber optic connectorhousing including an exterior body configured to be received in a fiberoptic adapter, a cavity defined by a rear portion of the connectorhousing, an anti-rotation seat coupled to the cavity, the anti-rotationseat including a plurality of longitudinally extending surfaces, andfirst and second contact lines positioned at a front of theanti-rotation seat adjacent a bore; the first and second contact linesbeing spaced apart on opposite sides of a longitudinal axis of theconnector housing and parallel to each other.

Another aspect of the invention relates to a fiber optic connectorincluding an optical fiber, a ferrule surrounding the optical fiber, ahub retainably engaging the ferrule, the hub including an anti-rotationportion, a housing defining an anti-rotation seat configured to engagethe anti-rotation portion of the hub, a spring disposed within a chamberdefined by the housing and coupled to the anti-rotation seat, the springbiasing the ferrule through the bore of the housing, and an alignmentarrangement formed by the connector, the alignment arrangement includingfirst and second tapered regions formed on one of the hub and thehousing, and also including first and second parallel contact linesformed on the other of the hub and the housing, the first and secondparallel contact lines and the first and second tapered regions beingspaced apart on opposite sides of a longitudinal axis of the connector,wherein the first tapered region engages the first contact line and thesecond tapered region engages the second contact line when the hub andferrule are in a first rotational position relative to the housing sothat an end of the optical fiber is maintained at a known orientationwith respect to the longitudinal axis of the connector.

Yet a further aspect of the invention relates to a method for using afiber optic connector comprising steps of: providing a ferrulesurrounding an optical fiber with a hub retainably engaging the ferrule,the hub including opposing first and second tapered portions; providinga housing including a first contact line positioned to engage the firsttapered portion and a second contact line positioned to engage thesecond tapered portion; pushing the ferrule back to disengage the firstand second tapered portions of the hub from the first and second contactlines of the housing; and releasing the ferrule so that the firsttapered portion engages the first contact line and the second taperedportion engages the second contact line, thereby retaining the opticalfiber at a known orientation with respect to the longitudinal axis ofthe connector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example embodiment of a fiber opticconnector made in accordance with the present invention.

FIG. 2 is an exploded view in perspective of the example connector shownin FIG. 1.

FIG. 3 is a side view of the example connector shown in FIG. 1.

FIG. 4 is a cross-sectional view taken along line C-C of the connectorshown in FIG. 3.

FIG. 5 is a rear view of the connector of FIG. 1 showing the fronthousing with the hub and ferrule included.

FIG. 6 is an expanded view of a portion of the front housing of theconnector of FIG. 5 showing the engagement of the anti-rotation portionof the hub with the anti-rotation seat of the front housing.

FIG. 7 is an expanded view of a portion of the connector of FIG. 4showing the engagement of the anti-rotation portion of the hub with thecontact lines of the anti-rotation seat.

FIG. 8 is a rear view of the connector of FIG. 1 showing the fronthousing with the hub and ferrule removed.

FIG. 9 is an expanded view of a portion of the front housing of theconnector of FIG. 8 illustrating the contact lines of the anti-rotationseat of the front housing.

FIG. 10 is a perspective view of an example embodiment of a hub andferrule assembly and an example anti-rotation seat including contactlines shown in isolation and made in accordance with the presentinvention.

FIG. 11 is a perspective view of the hub and ferrule assembly and theanti-rotation seat of FIG. 10 shown in an engaged position.

FIG. 12 is an enlarged cross-sectional side view of a ferrule and fiberof an angled physical contact (APC) connector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to exemplary aspects of the presentinvention that are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

FIGS. 1-3 illustrate an example embodiment of a connector 100 made inaccordance with the present invention. The connector 100 includes afront housing 110, a rear housing 140, a crimp ring 395, and a boot 150with a bore 152. Also included is a hub/ferrule assembly 120 with a hub122 and a ferrule 124. The hub 122 includes an anti-rotation portion 128and an elongated cylindrical rear portion 123. The hub 122 is connectedto the ferrule 124, such as with adhesive or an interference fit. Aspring 130 is also provided. A fiber optic cable 101 is shown includinga fiber 102 and an inner jacket 103. A reinforcing layer 400 and anouter jacket 401 surround the fiber 102 and the inner jacket 103. Thecrimp ring 395 secures the reinforcing layer 400 to the connector 100.

The connector 100 includes a spring-biased pivoting front cover 105which biases the cover 105 toward the closed position (as shown in FIG.3) or the open position as the cover 105 is moved in a direction F.Further details of the exterior features of the connector 100 and matingadapter are shown and described in U.S. Pat. No. 6,142,676, thedisclosure of which is hereby incorporated by reference. A latch 107latches connector 100 to the adapter. Guides 108 engage rails on theadapter to guide the connector 100 into the adapter.

The connector 100 may be tunable so that the ferrule and hub assembly120 may be pushed back, rotated, and released to tune the connector.Alternatively, the connector 100 may not be tunable. The presentinvention is applicable to tunable and non-tunable connectors.

Referring now to FIGS. 4-6, the front housing 110 of the connector 100extends along a longitudinal axis 200 and defines an anti-rotation seat112 and a cavity 114. The ferrule 124 extends through a front bore 116of the front housing 110 and includes a passage 118 extending through aface 125 of the ferrule 124. The anti-rotation portion 128 of the hub122 is slidingly engaged along the longitudinal axis 200 in theanti-rotation seat 112, as described further below.

The spring 130 surrounds the elongated cylindrical rear portion 123 ofthe hub 122. The spring 130 is captured between the anti-rotationportion 128 and a surface 146 of the rear housing 140. The spring 130functions to bias the anti-rotation portion 128 of the hub 122 into theanti-rotation seat 112 of the front housing 110. Because the ferrule 124is connected to the hub 122, the spring 130 also functions to bias theferrule 124 in a forward direction through the front bore 116. Theelongated cylindrical rear portion 123 of the hub 122 extends into thecavity 114 of the front housing 110. The hub 122 includes a passage 119extending along the longitudinal axis 200.

An outer surface 143 of the rear housing 140 is held engagingly in arear bore 117 the front housing 110. The rear housing 140 includes apassage 147. A rear portion 145 of the rear housing 140 extends alongthe longitudinal axis 200 into the bore 152 of the boot 150. The crimpring 395 is slid over the rear portion 145 and the reinforcing layer400, and crimped in place over the rear portion 145. Arms 151 of theboot 150 extend over tabs 144 formed by the rear portion 145 to hold therear housing 140 to the boot 150. A passage 152 extending through theboot 150 is coaxially aligned with passage 147 of the rear housing 140and passage 119 of the hub 122. The passage 119, in turn, is coaxiallyaligned with the passage 118 of the ferrule 124 and is sized to receivea bare fiber of a fiber optic cable. The rear housing 140 is held tofront housing 110 with an interference fit.

The cable 101, not shown in FIGS. 4-6, is extended through the passages152 and 147, and the fiber 102 is extended through the passages 118 andis glued to the ferrule 124. The jacket 103 extends through the passage119 and can abut the ferrule 124. The jacket 103 is glued to the hub122.

In the example embodiment, the anti-rotation portion 128 includesopposing surfaces 190 and 191 and opposing surfaces 192 and 193, as wellas edges 194-197. The anti-rotation portion 128 includes a plurality ofsides and the anti-rotation seat 112 defines a seat of a complementarygeometry, as shown in FIGS. 5 and 6. Engagement surfaces 181-188 formedby the anti-rotation seat 112 are configured to engage the opposingsurfaces 190-193 of the anti-rotation portion 128 of the hub 122. Theanti-rotation portion 128 and the anti-rotation seat 112 allow forsliding along the longitudinal axis 200, but prevent significantrelative rotation. Other mating shapes and configurations are alsopossible.

The complementary fit between the anti-rotation seat 112 and theanti-rotation portion 128 is designed to maintain the ferrule 124 in aspecified orientation with respect to the longitudinal axis 200 of theconnector 100. However, small variations in tolerances between theanti-rotation seat 112 and the anti-rotation portion 128 may cause theferrule 124 to become misaligned a few degrees with respect to thelongitudinal axis 200, thereby causing the face 125 of the ferrule 124to be slightly misaligned, increasing the insertion loss when theconnector 100 is mated to another connector through an adapter. Suchmisalignment can occur during initial assembly. Such misalignment canalso occur when an end face of an APC connector is mated with an endface of another APC connector, and then one connector is removed. Thespring bias returns the ferrule 124 and the hub 122 to the frontposition. The longitudinally extending surfaces of the anti-rotationportion 128 and the anti-rotation seat 112 maintain the generalrotational positions of the hub 122 and the front housing 110, but smallvariations may be introduced. If not corrected, the next connection ofthe connector may result in rotationally misaligned end faces.

Referring now to FIG. 7, an enlarged view of a portion of the connector100 is provided. Specifically, engagement of the anti-rotation seat 112and the anti-rotation portion 128 of the hub 122 is shown. Theanti-rotation portion 128 includes tapered surfaces or regions 220 and221 which extend at an angle with respect to the longitudinal axis 200to the end face 225 of the anti-rotation portion 128. These taperedregions 220 and 221 engage contact lines 215 and 216, respectively,formed in the anti-rotation seat 112. The contact lines 215 and 216function to guide and maintain the anti-rotation portion 128 of the hub122 in proper alignment with respect to the longitudinal axis 200. Withthe anti-rotation portion 128 of the hub 122 properly aligned, the face125 of the ferrule 124 and associated fiber 102 will also be properlymaintained in alignment. Alternatively, it is possible to form contactlines 215 and 216 on the anti-rotation portion of the hub 122 and toform tapered surfaces 220 and 221 on the anti-rotation seat 112 of thehousing 110.

The contact lines 215 and 216 are shown in FIGS. 7 and 8, which providerear views through the bore 117 of the front housing 110 with the huband ferrule assembly 110 removed. Each contact line comprises twoseparate and longitudinally-aligned edges formed by the anti-rotationseat 112. The contact line 215 is positioned opposite to and parallelwith the contact line 216 so that when the tapered regions 220 and 221engage the contact lines 215 and 216, the anti-rotation portion 218 isheld at a known orientation with respect to the longitudinal axis 200.If the hub 122 becomes misaligned when the hub 122 is spaced fromcontact 215 and 216, re-engagement of the surfaces 220 and 221 with thelines 215 and 216 caused by the spring bias will result in slightre-twisting or other physical correction of the hub 122 to the at restaligned position.

The anti-rotation seat 112 may also include a second set of parallelcontact lines 217 and 218. This second set of contact lines 217 and 218is positioned at a 45-degree angle about the longitudinal axis 200 withrespect to the set of contact lines 215 and 216. The second set ofcontact lines 217 and 218 can be used to provide additional rotationalpositions for the ferrule 122 and associated fiber 102 for tuning. Adescription of how the connector 100 may be tuned, if desired, isprovided below.

Lines 319, 320, 321, and 322 may preferably, but need not, be formed sothat they act as non-contact lines rather than contact lines. This isaccomplished by, for example, making a dimension G extending betweencontact lines 215 and 216 slightly smaller in size than a dimension Hextending between non-contact lines 319 and 320. In this configuration,when the hub 122 is biased towards the front of the housing 110, thetapered regions 220 and 211 engage the contact lines 215 and 216 becauseof the smaller dimension G between them. The hub 122 therefore fails tocontact the non-contact lines 319 and 320 because of the largerdimension H. It is preferably to include non-contact lines 319, 320,321, and 322 so that manufacturing tolerances for the anti-rotation seat112 and the anti-rotation portion 128 can more easily be met.

The engagement between the contact lines of the anti-rotation seat andthe tapered regions of the anti-rotation portion of the hub isillustrated in FIGS. 10 and 11. In FIG. 10, a representation of aportion of an anti-rotation seat 112′ is shown. The anti-rotation seat112′ includes contact lines 215′ and 216′ and bore 116′. The hub 122 andassociated ferrule 124 are shown spaced apart from the anti-rotationseat 112′.

In FIG. 11, the hub 122 is shown engaged with the seat 112′. The taperedregions 220 and 221 engage the contact lines 216′ and 215′,respectively. Held in this position, such as by the spring 130 (notshown), the hub 122 is aligned with respect to the anti-rotation seat112′ and the longitudinal axis 200 of the connector 100. With the hub122 aligned in this manner, the face 125 of the ferrule 124 is alsomaintained in alignment with respect to the longitudinal axis 200.Therefore, the ferrule 124 and the optical fiber 102 (not shown)extending from the passage 119 through the ferrule 124 are maintained ata known orientation with respect to the longitudinal axis 200 of theconnector 100 so that the ferrule 124 of the connector 100 can mate witha ferrule of an opposing connector through an adapter. Should the hub122 become misaligned when separated from the seat 112′, uponre-engagement of surfaces 220 and 221 with lines 215′ and 216′,realignment results.

The anti-rotation portion 128 further includes tapered regions 222 and223 positioned opposite to and in a parallel arrangement with respect toone another so that the hub 122 can be pushed or pulled, rotated aboutthe longitudinal axis 200 of the connector 100, and then re-engage thecontact lines 215′ and 216′ on the tapered regions 222 and 223.

Tuning of the connector 100 is accomplished by longitudinally pushingthe ferrule 124 against the spring bias until the longitudinallyextending surfaces of the anti-rotation seat 112 clear the anti-rotationportion 128 of the hub 122. Then hub 122 is rotated to a second positionto re-orient the ferrule 124 relative to the front housing 110. In theexample embodiment, there are 8 selectable positions for tuning. Feweror more positions can be included, if desired. Tuning can be by anymethod useful to determine the desired rotational position of theferrule 124 in the connector 100. Once the ferrule 124 has been rotatedto the desired rotational alignment, the ferrule 124 can be released andthe spring 130 can once again bias the anti-rotation portion 128 of thehub 122 into the anti-rotation seat 112 of the front housing 110,thereby preventing further rotation. The connector 100 is tuned withrespect to the exterior structure matable with an adapter of the type inU.S. Pat. No. 6,142,676. The configuration of the connector 100 is suchthat it is keyed so that it can only be received in the adapter in oneorientation.

The orientation of the face 125 of the ferrule 124 may be particularlyimportant for an angled physical contact connector, in which the endface of the ferrule must be maintained at a specified angle with respectto the longitudinal axis of the connector. In one example embodiment,the angle α is eight degrees, as shown in FIG. 12. Through use of thecontact lines on the anti-rotation seat and the tapered regions on theanti-rotation portion of the ferrule, the proper orientation of theferrule and associated fiber may be maintained in angled physicalcontact connectors and other connectors.

The above specification, examples and data provide a completedescription of the manufacture and of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

1. A fiber optic connector comprising: an optical fiber; a ferrule surrounding the optical fiber; a hub coupled to the ferrule, wherein the hub includes an anti-rotation portion including: four opposing surfaces; and four tapered regions, one of the four tapered regions extending from each of the four opposing surfaces at an angle with respect to a longitudinal axis of the connector, each of the four tapered regions extending towards a front end of the optical fiber; a housing defining an anti-rotation seat including: a first set of parallel contact lines; a second set of parallel contact lines positioned at a forty-five degree angle with respect to the first set of parallel contact lines, wherein the first and second sets of parallel contact lines are positioned at a front of the anti-rotation seat adjacent a bore defined by the housing through which the ferrule extends; and first and second sets of non-contact lines, wherein a length dimension of the first and second sets of parallel contact lines is shorter than that of the first and second sets of non-contact lines; and a spring disposed within a chamber defined by the housing, the spring biasing the ferrule through the bore of the housing; wherein, as the spring biases the ferrule, two opposing tapered regions of the four tapered regions of the hub engage one of the first and second sets of parallel contact lines so that the front end of the optical fiber is maintained at a known orientation with respect to the longitudinal axis of the connector. 